Disappearing typewriter shelf



Jan. 18, 1955 A. w. RICHARDS 2,699,979

DISAPPEARING TYPEWRITER SHELF MINIMUM" M1.

B HM sm@ ATTORNEY Jan. 18, 1955 A. w. RICHARDS DISAPPEARING TYPEWRITER SHELF Filed June l5, 1951 Sheets-Sheet 2 K 1W! Ullllnl Il msm-Amd ATTORNEY Jan. 18, 1955 A. w. RICHARDS 2,699,979

DISAPPEARING TYPEWRITER SHELF 3 Sheets-Sheet 3 Filed June l5, 1951 lIMWWW United States Patent() DISAPPEARIN G TYPEWRITER SHELF Archer W. Richards, Chagrin Falls, Ohio, assiguor toV Republic Steel Corporation, Cleveland, Ohio, a corporation of New Jersey Application June 15, 1951, Serial No. 231,838

20 Claims. (Cl. S12-29) be moved outwardly and upwardly to a position for use of the typewriter supported upon it. As employed in a desk pedestal, the typewriter shelf mechanism thus permits the typewriter to be concealed and enclosed or otherwise protected when not in use, yet affords ready displacement of the shelf to a working position, i. e. where the shelf supports the typewriter at the side of the desk in proper location for use by a typist.

Shelf lifting mechanisms of this character are well known, generally embodying a supporting shelf with associated means permitting both horizontal and vertical displacement of the shelf, the mechanism being commonly arranged so that in bringing the shelf out of the pedestal cavity, the first motion causes the shelf to be pulled outwardly at the lower position, whereupon the operator may then lift it (and the supported typewriter) to the upper position for use, horizontal track means or the like being customarily provided upon which a carriage bearing the shelf is adapted to travel for the horizontal motion, and supplemental means, usually counterbalanced with a spring, being also provided to permit elevation of the carriage (preferably both the track and carriage) to the upper locality. Provision is commonly made to prevent any upward motion of the shelf until it has been fully withdrawn in a horizontal direction, and` likewise to prevent any horizontal, inward motion, once the shelf has been raised to any extent from-the lowest level; and supplemental means are also provided for locking or retaining the shelf in the uppermost position.

For example, in one known and particularly effective type of shelf mechanism, the shelf itself is mounted on a carriage which is adapted to ride on tracks at the sides of the desk pedestal cavity, the carriage being fixed to the shelf so as to underlie the rearmost portion of the latter. When the shelf is drawn forward the carriage is thus advanced to the outermost or front end of the tracks, where it releases a latch or latches that normally serve to retain the tracks in lowermost position. Vertical tracks are also provided at the sides of the cavity adjacent the entrance, with accompanying spring-balancing mechanism so arranged that the horizontal tracks, carriage and shelf may be elevated as a unit when the latches have been released. The spring mechanism comprises a horizontally extending coil spring which acts through-pinions meshing with vertical racks alongside the vertical tracks, the spring being wound so as to bias the traveling assembly in an upward direction but beingarranged to unwind and diminish in tension as the assembly rises. Finally, curved notch means are provided adjacent the upward path of the carriage at the top, so that the assembly may be rocked slightly upward and then rearward to seat appropriate holding studs in the notches and thus maintain the shelf securely in uppermost position, i. e. until by a positive, reverse operation it is released for replacement in the cavity.

In this example of prior apparatus, means are also provided to prevent any rearward motion of the carriage on the horizontal tracks after the assembly has been raised from the bottom position, such means being effective throughout all upper positions of the shelf. Conveniently, for instance, certain of the studs which are mounted on the carriage and which as mentioned above serve to lock out all upper positions of the movable 2,699,979 Patented Jan. 18, 1955 the assembly in upper position, may be arranged to project ahead of vertical flanges on the vertical tracks and thus constitute the described lock against inward movement of the shelf throughout the vertical path of travel. It will be understood that the described sequence of motions and the arrangements preventing unwanted displacement, are desirable not only to afford ease of operation but particularly to avoid jamming or other damage to the typewriter.

In apparatus of this type the carriage or equivalent support for the shelf necessarily occupies a substantial distance, say 6 or 7 inches, in the fore and aft direction, i. e. along the horizontal tracks, and since the horizontal tracks terminate at the front of the desk cavity, and the carriage cannot move off the tracks, a corresponding area of the shelf (or of shelf space) remains within the cavity even when the shelf is moved to its outermost position. In consequence the exposable or useful extent of shelf must be shorter than the fore and aft dimension of the cavity by an equivalent amount, e. g. at least 6 inches, or indeed somewhat more where the front cavity frame and desk top represent s'ome overhang. At the same time, the requirements of usable space on the shelf, particularly in the fore and aft direction, are determined by the size of the typewriter, the clearance needed for its moving parts, and the convenience of typing operation. In consequence the minimum width or fore and aft dimension of the desk itself is thus determined by the actual requirements of typewriter shelf space, plus the more or less lost or wasted space described above, including the longitudinal carriage dimensions, Various modern typewriters, particularly those of electrically operated type, require relatively large shelf areas, yet economy of ofiice space, and likewise economy of desk manufacture, make it undesirable to increase the width of desks any more than is absolutely necessary. Even where unusual extent of shelf space is not needed, similar considerations of desk room and placement of office furniture have demanded narrower than wider desks, but the limitations of the shelf supporting mechanism have imposed an unduly large minimum on desk width.

It is therefore an important object of the present invention to provide an extendable typewriter shelf apparatus, i. e. a new and improved structure wherein the effective supporting shelf may be advanced further from the pedestal or other cavity than has heretofore been possible. A further and corresponding object is to provide an improved shelf arrangement embodying a horizontally slidable carriage with a shelf and cooperating shelf structure, having means of an extendable nature to achieve greater, yet fully secure projection of the shelf from the enclosure. At the same time, further objects are to afford extendable shelf apparatus which is positive in action, and entirely safe and foolproof, against improper movement such as might jam or otherwise damage the typewriter.

Other objects are to afford apparatus of the character stated, embodying an extendable shelf mechanism with appropriate safety provisions, which may be readily embodied in shelf operating mechanism of presently available character, i. e. without appreciable change in the structure or function of the present operating parts of the mechanism. l

To these and other ends, presentlyL preferred embodiments of the invention embrace a shelf element which is movably arranged upon a carriage of the character described above, the shelf being mounted to slide horizontally, in the same fore and aft direction as the carriage, but relative to the latter, while being supported by appropriate rails or framework on the carriage. In cooperation with such shelf, which may thus be adapted for withdrawal to a distance say, several inches greater than the shelf rigidly mounted on the carriage, the invention preferably includes means responsive to the position of the shelf for preventingv any elevation of the carriage and shelf from the bottom position until both the carriage and shelf have beenvadvanced to their outermost limits, further locking means being included to prevent inward displacement of the shelf relative to the carriage, as well as inward displacement of the carriage itself, throughassembly, the lastmentioned means being only releasable (after an upward displacement of the shelf) upon the return of the assembly to the lowest level, and upon its safe retraction into the pedestal cavity.

More specifically, the preferred apparatus of the invention embraces supplemental locking means cooperating with the shelf, the carriage and the tracks upon which the latter rides, to prevent substantial outward displacement of the carriage until the shelf has rst been moved outwardly to the desired limit, relative to the carriage. The described means include further instrumentalities locking the shelf in its outward position relative to the carriage during all subsequent travel of the carriage, i. e. during both the outward and upward movements of the latter, still further, positive locking means being included to safeguard the shelf against inward displacement (relative to the carriage) once the whole assembly has reached the outer position and throughout all parts of its upward path. All of the locking and retaining means are arranged to be releasable only upon restoration of the correisponding parts to safe positions, means being included such that rearward displacement of the shelf relative to the carriage can only be achieved when the latter has substantially reached the innermost limit of its horizontal travel in the bottom of the enclosure.

By way of specific example, a presently preferred embodiment of the invention is described below and illustrated in the accompanying drawings wherein:

Fig. l is a plan view of the shelf and associated suspension structure, with certain portions of the shelf cut away;

Fig. 2 is a vertical section on line 22 of Fig. l',

Figs. 3 and 4 are fragmentary, enlarged vertical sections respectively taken on lines 3 3 and 4--4 of Fig. 2;

Fig. 5 is an enlarged elevational View, partly in vertical section along the lower track of Fig. l, showing the complete shelf suspension mechanism;

Fig. 6 is an enlarged, fragmentary, elevational view showing the carriage and shelf structure in a position after the shelf has been advanced from the location shown in Fig. 5;

Fig. 7 is a view similar to Fig. 6 showing a further position of the parts after preliminary advance of the carriage;

Fig. 8 is a view similar to Fig. 7 but showing the carriage and shelf at the outermost end of their horizontal travel; and

Fig. 9 is an enlarged fragmentary, vertical section on line 9-9 of Fig. 5.

Referring first to Figs. l and 5, it will be understood that the entire shelf mechanism is designed to be mounted in a suitable, forwardly-accessible enclosure, such as the conventional cavity or cabinet of a desk pedestal, e. g. in desks of appropriate metal, wood or other construction. Here for example, the pedestal cavity is represented by its rear wall 21, floor 22 and roof 23, arranged to afford a full-size, front opening as indicated at 24, which may be closed by the usual hinged door, not shown. The illustrated example of desk cavity, being embodied in a steel desk structure, includes suitable reinforcing channels, including a rear horizontal channel 26 and upper and lower front horizontal beams 27 and 28, the latter and other structural parts of the desk cavity being appropriately employed for mounting the shelf suspension mechanism.

The shelf suspension apparatus comprises a carriage assembly 30 which includes a pair of carriage body members 31, 32 disposed parallel to each other at opposite sides of the apparatus and each provided with a pair of longitudinally spaced rollers 34. The pairs of rollers 34 of the carriage bodies 31, 32 are respectively disposed to travel in box tracks 3S, 36, i. e. horizontally facing channels which extend from front to rear of the cavity at the outer sides of the carriage assembly. At their rear or inward ends the box tracks are tied by a cross member 38 and at their forward ends are respectively secured to vertically movable carriers, Fig. 5 showing the carrier 40 to which the outer side of the track 36 is mounted. As will be understood, the track 35, shown in vertical section in Fig. 5, is secured to an identical vertical carrier which is disposed on the outer side of track 35 and thus not visible in Fig. 5, the identical position of the carrier 40, however, (for the other track 36 concealed by the track 35) being adequate to illustrate the position and function of both carriers. It will be appreciated that the parts thus far described represent presently available and well known mechanism, requiring no detailed explanation here.

The basic mechanism also includes vertical guide tracks at the sides of the apparatus adjacent the front cavity opening 24, respectively supporting the vertical carriers. These guide tracks, identical at opposite sides but arranged in oppositely facing relation, are thus represented by one of them, designated 42 and including a channel portion 43 receiving vertically spaced rollers 44 on the carrier 40. Each vertical track assembly 42 also includes a vertical rack 45 with which a pinion 46 meshes, the pinion being carried by the corresponding carrier 4t), and the pinions being arranged to unwind and wind a coil tension spring arrangement (not shown) which is housed in the U-shaped transverse channel 47. This channel extends between the carriers, i. e. across the front of the mechanism, to complete the horizontal framework constituted by the rails or tracks 35, 36, and the rear tie 38. As will be understood, the spring is conventionally arranged under wound tension in all positions, becoming further wound by downward travel of the vertical carriers to the lowermost position of the pinion 46 as seen in Fig. 5, and being somewhat unwound as the carriers move upward along the track assemblies represented by the track 42.

Each of the carriage bodies 31, 32 has projecting from its side face, above the corresponding track 35 or 36, longitudinally spaced, forward and rear pins or studs 48, 49.. When the carriage is moved to the outer or forward posltion, the front pin 48 then passes ahead of the lower end of a vertical flange on the adjacent upright track, i. e. as indicated by the flange 50 for the track 42 in Figs. 5 and 8, Fig. 8 showing the stated forward position of the carriage. When the horizontal tracks 35, 36 and carriers 40 are then moved upward (with the carriage 30), the forward pins 48 ride outside the anges, preventing any rearward motion of the carriage on the tracks 35, 36. At the upper limit of the vertical travel of the assembly, appropriately disposed pairs of curved notches 52, 53 in the stationary structure (Fig. 5) are arranged to be engaged by the studs 48, 49 on each side, i. e. so that upon raising and rearwardly re-seating the movable assembly, the studs are seated in the notches, for firm but releasable support of the assembly in such position.

At the forward edge of the lower part of each of the vertical trackways, a spring-pressed latch 55 is disposed, including a detent surface 56 normally engaging the lower flange of the adjacent track 35 or 36, each such latch 55 being released (Fig. 8) when engaged by the forward wheel 34 of the corresponding side of the carriage 30. All of the further, specific parts above described are likewise components of the stated, known mechanism. As has also been explained or implied, the various horizontal and vertical tracks, carriage elements, rollers, and associated guiding and locking parts are exactly duplicated at the respectively opposite sides of the entire assembly, i. e. in oppositely facing relation and for identical function, so that the showing of different parts from respectively opposite sides in views such as Figs. 5 and 8 will suf-lice to illustrate the operative relation of a complete set of parts at either side, and indeed may be taken as representing such set of parts at one side alone.

The operation of the basic, known assembly will now be readily understood. Upon advancing the carriage 30 from its rearmost or closed position shown in Fig. 5, the carriagerbodies 31, 32 are moved forward to the position of Fig. 8, the wheels 34 being supported in the track 35 or 36 (at each side) and the forward wheel eventually striking and releasing the latch 55. Thereupon, as aided by the transverse tensioning spring (not shown) the entire assembly of the tracks and carriers 4G, with the carriage, may be moved upward, the studs 48 traveling outside the flanges 50 to prevent inward movement of the carriage. At the uppermost limit of travel, the assembly is releasably but securely held by the engagement vof the studs 48, 49 in the notches 52, 53. Replacement of the assembly to its original position of Fig. 5, involves reverse operations, i. e. rst releasing the studs 48, 49 from the notches 52, S3 and moving the carriage forward so that the stud 48 is positioned outside of the flange 50E Thereupon the operator moves the carriers 48 downward by depressing the carriage and horizontal tracks against the spring tension, and then moves the carriage back inward along the tracks as soon as the studs 48 have cleared the lower ends of the flanges 50. In the downward travel, the lower corner of the track 35 first cams the latch 55 outwardly, so that after the wheel 34 has moved inward the detent surface 56 may re-seat over the lower flange of the track.

In prior arrangements, the typewriter-supporting shelf has been mounted directly on and between the carriage elements 31, 32 for movement into and out of the cavity 20 by the operations just described, but the useful length of exposed shelf surface is limited to the fore and aft length of the cavity 20 diminished by the length of the carriage body parts 31, 32.

In accordance with the present invention, there is provided a movable shelf 60 (Figs. l to 5 and 9) which is arranged to slide lengthwise of the cavity 20 on a supporting frame 62 which is in turn mounted upon the carriage elements 31, 32 and thus constituted part of the carriage 30. The illustrated example of the sliding shelf 60 is conveniently made of sheet steel or the like, including a flat top or upper surface 64 of rectangular shape, and integral downwardly extending skirt portions along its edges, e. g. constituted by the side walls 65 at opposite sides and forward and rear walls 66, 67, the essentially integral and continuous connection of the top and walls providing a rigid, inverted tray-like structure which may be further reinforced as desired, for example by the shallow, flanged channel section 68 welded alongthe underside of the top 64.

To support the shelf 60, the underlying frame 62 comprises a pair of spaced, parallel tracks or rails 70, each consisting of a channel member disposed to -underlie the shelf along the inner side of a corresponding side wall or skirt 65, the channel members 70 being arranged with their open sides facing the center of thev assembly. Near their forward ends, the members 70 are tied and braced by a transverse, wide channel member 72 having flanges at its ends that are welded to the respective webs of the members 70, while between the rear portions of the rails 70, another channel member 74 is secured with its flat bottom web overlying the lower flanges 73 of the members 72. The member 74 has upstanding flanges 76, 77 which thus extend transversely between the member 70 and which are spaced lengthwise of the apparatus, the rearmost flange 761-being arranged at the inner end ofthe assembly, outside the depending skirt 67 of the shelf 60. The frame 62 is thus a rigid rectangular structure constituted by the rails 70 and the transverse members 72, 74.

pieces both conveniently designated 78 are mounted respectively on the carriage members 31, 32, the upright wall portions of the members 78 being appropriately secured on the inner faces of the similar upright wall portions of the members 31, 32, and each of the members 78 having a horizontal flange 79, i. e. with the rail flanges 73 resting on the latter, by appropriate means such as a row of bolts 80, certain of the bolts also serving to secure the bottom web of the transverse channel 74 in the position described above. Thus the frame 62 is rigidly and securely associated with, and supported by, the carriage elements 31, 32, these elements and the frame thus constituting the complete carriage assembly 30 which is movable lengthwise of the tracks 35, 36 as described above.

The rear skirt 67 of the top 60 terminates a short distance inwardly of the side walls 65, leaving openings 82 at the back of the shelf, adjacent the corners, through which the side rails 70 of the frame may respectively pass, the shelf 60 being thus arranged to slide on the rails, i. e. from the position shown in Figs. l and 5, toward the right (Figs. 6 to 8).' Retention of the shelf on the rails 70 is aided by integral, underlying flanges 84 which project inwardly from the lower edge of the shelf side walls 65, beneath the track flanges 73 at localities of the latter ahead, (i. e. to the right as seen in Figs. l, 2 and of the carriage supporting members 78. The flange portions 84 also include upward retaining lips 85, and the flanges and lips 84, 85 also conveniently extend, for rigidity and reinforcement, along the bottom edge of the front shelf wall 66.

For maximum ease of operation of the shelf, ball bearing slide means are preferably included (Figs. l to 4) e. g. at localities spaced to afford secure support of the shelf in all positions which it and the carriage may assume. vThus a pair of upper and lower ball tracks 86,

86a are shaped in a channel element 86b which is mounted at the inside of each rail or track member 70 adjacent the forward end of the latter. The ball tracks 86, 86a, disposed as shown in the upper and lower corners of each rail 70, support corresponding bearing balls 87, 89, which engage the inner face of the shelf side wall 65, and respectively the inner face of the shelf top 64 and the inner face of the lower shelf flange 84. Suitable portions of the channel rail 70 are cut away to accommodate the balls, the ends 88 of thel cut-out regions thus constituting stops to retain the balls in the races thereby provided. At a further locality, spaced rearwardly from the ball supports just described, but somewhat ahead of the carriage member 78, a channel element 90 is mounted at the inside of each rail member 70, shaped to provide ball tracks 91, 92 respectively at the upper and lower corners of the member 70. The ball tracks 91, 92 respectively accommodate balls 93, 94 which engage the side wall 65 and respectively the shelf top 64 and the lower shelf flange 84. As in the structure associated with the ball races 86, the rail member 70 (at each side) is appropriately cut away to admit the balls 93, 94, the ends 95 of the cut-away portions constituting stops for the ball travel.

It will be understood that ball bearing supports as just described are provided at both sides of the shaft 60, e. g. as indicated respectively in Figs. 1 and 2, the parts being identically numbered. In consequence the shelf is effectively supported by the four balls 87, 89, 93, 94 at each side, the upper balls 87, 93 essentially serving to carry the weight of the shelf and its supported typewriter, and the lower balls 89, 94 affording adequate, frictionminimizing support against any tendency of the shelf to rock into a binding engagement between its flange 84 and the track flange73.

It will be noted that the rear skirt 67 of the shelf 60 projects into the channel 74, so that the sliding movement of the shelf is limited by the flanges 76, 77 of the channel. Sets of bumpers 96, 97 of rubber 'or the like are conveniently provided on the inner faces of the flanges 76, 77 to absorb the shock as the shelf is moved from one to the other of its limiting positions. For betterrrigidity at the localities of engagement with the bumpers, reinforcing angle pieces 98 are secured at corresponding localities of the inner side of the shelf skirt 67 and adjoining portion of the shelf top 64. Although other stop arrangements may be provided in some cases, the illustrated structure, including the flanges of the channel member 74, affords convenient stop means to limit the inward and outward displacement of the shelf relative to the carriage, the extension distance ofthe carriage being thus predeterminable by the width of the channel 74 between its flanges.

As indicated above, an important feature of the invention comprises supplemental locking means cooperating with the basic shelf suspension structure to prevent undesired displacement of the shelf and carriage. To that end, there is pivotally mounted on the outer side of each Aof the carriage body plates 78 a star cam 100 having three spaced teeth as shown and having an inwardly offset cam portion 102 disposed to engage edge regions of a cam or detent plate 104 secured on the outer side of the shelf skirt 65 near the rear end of the shelf. That is to say, the `main body of the cam is spaced outwardly from the carriage plate 78 so as to clear the cam plate 104, but the extension part 102, diametrically opposite the central tooth of the cam 100, projects from an inwardly turned part of the cam body so as to lie in the plane of the cam plate 104.

Means are conveniently provided to bias the cam 100 in a clockwise direction, for example a wire spring 105 wound around the cam pivot and secured at its ends respectively to the cam and the carriage element 31, the spring being sufficiently wound so that in all operating positions of thecam (e. g. as seen in Figs. 5 to 8 inelusive), it is resiliently urged to turn clockwise.

Cooperating with the star shape of each cam 100, a row of three teeth 106, 107, 108 (Fig. 5) are mounted on the upper face of each of the carriage-supporting tracks 35, 36, the teeth 106--108 being spaced for engagement with the teeth of the cam in the general manner of a rack and pinion when the carriage 30 is advanced along the tracks 35, 36, and being positioned at a rearward locality of the tracks, i. e. in engaging relation with the cam when the carriage is in its rear position. A further tooth or stop 110 is mounted on each kof the upper '7 surfaces of the tracks 35, 36, near the front end of the latter for engagement` with a tooth of the cat-n 100, as more fully described below. l

The detent plate 104 on the shelf has a lower horizontal edge surface 112 of considerable length, to be slidably engaged by a corner of the star cam projection 102 when the shelf is in its rearmost location as seen in Fig. 5. The plate 104 also has a curved cut-out or recess 113 at its rear lower corner, the edge of such recess including a straight portion 114 intersecting the under edge 112. The outer edge of the cam projection 102, extending generally transverse of a radius yof the cam, consists of a curved region 115 and a straight or ilat edge region 116, the mutual shapes of the cam plate recess 113-114 and the movable cam edge 11S-116 being such as to permit the cam portion 102 to swing aroundrin the plate recess (upon appropriate displacement of the shelf and carriage) into a position where the flat edge region 116 of the pivoted cam 100 seats against the at edge 114 of the cam plate recess.

Referring now more particularly to Figs. to 8 inclusive, the operation of the mechanism will be readily understood. It may be assumed that a typewriter (not shown) is mounted on the top surface 64 of the shelf 60, in such position that when the shelf and carriage are both fully advanced and elevated to the uppermost position, the typewriter will be in location for use. When not in use, the parts are all withdrawn into the desk cavity 20, such inoperative or original position being shown in full lines in Fig. 5. Here it will be seen that the shelf is at its rearmost location, the skirt 67 abutting the bumper 96, and the lower edge 112 of the cam plate 104 engaging a corner of the portion 102 of the movable cam 100, while the most clockwise tooth 120 of the cam abuts the rear edge of the central tooth 107 of the group 106-108 on the track 35. In this relation of the parts, no partial forward displacement of the shelf 60 can move the carriage 30, since the plate edge 112 holds the cam tooth 120 in carriage-arresting or locking engagement with the stationary tooth 107, the spring bias on the cam 100 cooperating to hold the cam part 102 against the plate edge 112.

In order to withdraw the typewriter from the desk cavity, the operator merely pulls the front end 66 of the shelf 60, thus sliding the shelf outward on its tracks 70. During at least a major part of this motion, the plate edge 112 slides along the corner of the star cam portion 102, continuing to keep the carriage locked in its rearmost position. When the recess portion 113 of the plate 104 reaches the corner of the star cam part 102, and 1s then moved further forward with the withdrawing operation on the shelf, the star cam 100, under the action of the spring 105, is free to turn a short distance clockwise. ln consequence upon withdrawal of the shelf to its outer limit relative to the tracks 70, i. e. when the rear skirt 67 engages the forward bumpers 97, the several parts occupy the position shown in Fig. 6, the tooth 120 of the cam having now moved around to abut the leading face of the stationary tooth 106.

The carriage 30 is now released, so that further pull on the shelf initiates outward movement of the carriage along the tracks 35, 36. As the operator thus' continues to pull the shelf, the carriage advances and the teeth of the star cam accordingly turn gear-wise relative to the stationary teeth 106-108 so as to swing the cam into the position shown in Fig. 7, the carriage being now somewhat advanced from its rearmost position. During the carriage movement just described, the curved portion 115 of the star cam has swung around clockwise in the recess 113 of the plate 104 (the radius of the edge 115 being appropriately shorter than the radius of the rearmost portion of the recess), so that the ilat edge 116 of the cam projection has seated lirmly against the correspending at edge 114 of the recess.

lt will be noted that the described means, including the star cam and other parts, effectively prevent any ad- Vance, or at least any substantial advance of the carriage until after the shelf has been first moved, relative to the carriage, to its extreme outward position. While the unlocked position of the star cam in Fig. 6 may be c mestiere reces's113 and thus in efec't positively forcing the shelf to its forwardmost position. Hence even if there is any tendency of the shelf to stick on the rails 70 (such being ordinarily obviated by the ball bearing supports), the locking means affords positive assurance that the shelf is fully advanced on the carriage at least by the time that the carriage has made the slight advance to its position of Fig. 7.

Further withdrawing force on the shelf then continues to move the carriage forward, i. e. to the right as seen in Figs. 5 to 8. The spring 105 holds the star cam 100 in its furthest clockwise position, and thus with the edges 116 and 114 in rmly seated engagement, throughout the entire path of outward travel of the carriage. This relation of the parts affords an effective lock, to prevent any rearward motion of the shelf relative to the carriage; any tendency toward such motion is positively opposed by the direct engagement of the stated cam edges. Accordingly, the shelf and carriage assembly are ultimately pulled to the outermost position illustrated in Fig. 8, it being remembered that the supporting tracks are maintained in their lower location throughout the preceding operations, by the engagement of the latch 55.

As shown in Fig, 8, the carriage is now advanced to a position where the forward stud 4S lies in a vertical plane outside the outer edge of the vertical guard flange 50. At the same time, the forwardmost tooth 122 of the star cam has now come into abutment with the forward stationary tooth 110 on the rail 35. This not only affords an effective Vouter stop for the carriage (in addition to or as an alternative for such outer stop means as may be customarily provided in the basic shelf suspension mechanism) but cooperates to hold the star cam 100 positively in the position shown. ln other words when the carriage is in its outer position, the locking abutment of the star cani edge 116 and shelf cam edge 114 is maintained both by the spring 105 and the positive holding means constituted by the tooth 110.

The forward wheel 34 of the carriage having at the same time released the latch 55 (Fig. 8), the entire assembly, including the rails 35, 36 and the vertical carriers d0, may be moved upward, As already explained, the stud d8, during such upward motion, rides outside or forwardly of the flange 50, positively preventing any inward motion of the carriage on the rails 35, 36. At the same time the positive lock constituted by the engagement of the star cam 100 with the tooth 110 and the plate 104 prevents any inward displacement of the shelf relative to the carriage. Such relationships prevail throughout all upper locations of the assembly, including the operating position indicated by the broken line representative of the carriage element 31 at the upper righthand corner of Fig. 5

It will be understood that the conventional spring means (not shown) of the basic suspension mechanism facilitates upward motion of the assembly and likewise avoids any damaging shock on inadvertent release of the parts. As also explained, the releasable retention of the shelf assembly in the uppermost, operating position, is afforded by engagement of the studs 43, 49 in the notches 52, 53 of the stationary structure. So extended and elevated, the shelf 60 now presents the typewriter in position for operation.

When it is desired to replace the typewriter in the cabinet, a reverse sequence of operations is followed. The assembly is rst released from the notches 52, 53 by rocking it slightly outward and upward, whereupon the shelf, carriage and carrier may be pushed down, guided by the vertical track means 42, until the position of Fig. 8 is again reached. Here the outer stud 4S is now disposed to clear the lower end of the vertical ange 50, so that an inward push on the typewriter shelf 60 will slide the carriage inward along the rails 35, 36, the latches 55 immediately returning to locked position, holding the rails down by engagement of the detent surfaces 56. During essentially the complete inward motion of the carriage, the star cam 100 remains in the position of Figs. 7 and 8, with the locking edges 116-114 engaged so as to prevent any inward movement of the shelf on the tracks 70.

v)Finally as the position of Fig. 7 is reached, the teeth of the star cant are again engaged with the successive stationary teeth 108--106- During the final inward displacement of the carriage from Fig. 7 to Fig. 6, the star cam is thus rocked counterclockwise, unlocking the shelf. Final inward push on the shelf may now, and only now, effect its inward motion on the track 70, `until the shelf skirt 67 comes to rest against the rear bumper 96. During this movement of the shelf, the lower plate edge 112 rides upon and over the upper corner of the star cam projection 102, turning the cam further counterclockwise into the carriage-locking relation of Fig. 5, the parts thus now being fully restored to their original withdrawn or closed position.

While reference above has sometimes been made only to the cam, teeth and detent means on one side of the shelf 60, all of the parts are preferably duplicated on the other side, to function identically and simultaneously.

It will be noted that the entire operation of withdrawing the shelf and restoring it is effected by manual engagement of the shelf alone, the latter indeed being conveniently so shaped as to mask the carriage and its shelfsupporting rails '70. However, the locking action of the several parts is such that no significant displacement of the carriage can occur, i. e. outward from the position of Fig. 5, until the shelf has iirst been withdrawn. The whole operation of use of the mechanism precisely simulates the normal and conventional mode of actuating a typewriter shelf suspension, so that the operator need only draw the shelf out and upward, and then restore it, in the accustomed way. The mechanism thus provides a special extending shelf arrangement, yet the locking features prevent any danger of damage to the typewriter, i. e. in insuring that both the shelf'and carriage are fully extended before any upward motion can take place, and likewise that upon restoring the parts, no inward motion of either shelf or carriage may occur until after the assembly has reached its lowermost position where the typewriter is sure to clear the top of the cavity 20. At all times, moreover, the shelf 6i) is sturdily supported, to carry the heavy weight of a typewriter.

It will be noted that the structure and design of the parts may, if desired, be conveniently such that when there is no load on the shelf 60 and the latter is fully retracted (Fig. it assumes a slight upward and outward tilt; such tilt compensates for any slight elastic deformation cf the shelf-supporting parts, and particularly for the clearance and play in the various bearing elements, so that when a heavy typewriter is mounted on the shelf, and the latter is brought out toits upper and outer location, it will assume a truly horizontal position, firmly and securely supported by the carriage structure.

It will be appreciated that the extent of forward displacement of the shelf may be predetermined to occupy any of a considerable range of distances. For example, with a specific, presently available basic suspension structure of the sort shown (including carriage members 31, 32 about 6 inches long) useful shelf extension movements up to 3 inches or so have been provided. In many cases, however, longer shelf extension (i. e. a longer spacing between bumpers 96, 97) may be effectively achieved with the described means, especially when the carriage has a longer distance between its forward and rear wheels 34. For certain present purposes, an extension of 2 or 3 inches is ample, e. g. in permitting accommodation of large, modern typewriters in desks of conveniently limited size. f

The reliability of the locking means, moreover, extends even to various unusual situations. For example, even if the carriage (on withdrawal of the shelf) should move slightly from rearmost position before the shelf reaches the position (on it) of Fig. 6 (an unlikely situation, since the friction of the ball-carried shelf is normally less than that of the carriage) and then the star cam should come to rest before its edge 116 is fully opposite the shelf cam edge 114, the star cam will nevertheless have sufficiently locked the shelf so that the ultimate abutment of the cam tooth 122 with the stop 110 (Fig. 8) will insure nal and complete locking with the shelf fully advanced on the carriage. The spring 105 on the star cam, a feature of present preference (a1- though it may be omitted in some cases, especially if there is some friction in the cam pivot), also affords further insurance against unusual occurrences; for example, evenv if the cam tooth 122 should not remain in tight abutment with the stop 110 when the shelf is in its upper and outer position, the spring will prevent the vibration due to typing from loosening the cam. The spring 105 also provides additional certainty that the cam tooth i6 122 will be in proper position to strike the stationary tooth or stop 108 on the return trip o f the carriage.

It is to be understood that the invention is not lim-v ited to the specific apparatus herein shown and described but may be embodied in other forms without departure from its spirit.

I claim:

1. In a disappearing shelf mechanism, in combination with a carriage and supporting means and guiding means for guiding the carriage, respectively through successive forward and upward displacements, a shelf supported on the carriage and displaceable relative to the carriage between rear and forward positions, and releasable locking means on the carriage engageable with cooperating means on the supporting means and held in locking position by the shelf in its rear position, for locking the carriage, against forward advance from a predetermined rearward position on the supporting means, said locking means being shiftable to a position releasing the carriage, upon predetermined forward displacement of the shelf relative to the carriage.

2. In a disappearing shelf mechanism in combination with a carriage and supporting means and guiding means for guiding the carriage, respectively through successive forward and upward displacements from a lower, rear position, a shelf supported on the carriage and displaceable relative to the carriage between rear and forward positions, and locking means including an element on the carriage and cooperating means on the supporting means adapted to'prevent advance of the carriage from a rearward position, under control of the shelf, said element being shiftable to carriage-releasing position upon predetermined forward displacement of the shelf, said cooperating means on the supporting means being adapted for shifting the locking element into a further position preventing rearward displacement of the shelf relative to the carriage, in response to forward advance of the carriage from its aforesaid rearward position.

3. In a disappearing shelf mechanism, in combination with a carriage and supporting means and guiding means for guiding the carriage, respectively, through successive forward and upward displacements from a lower, rear position, a shelf supported on the carriage and displaceable relative to the carriage between rear and forward positions, a locking device on the carriage movable against a portion on the shelf to prevent rearward displacement of the shelf from its forward position on the carriage, and means effective in response to advancement of the carriage to its forwardmost position, for positively holding said locking device against the shelf portion throughout all upward positions of the carriage and shelf.

4. In a disappearing shelf mechanism, in combination with a carriage land supporting means and guiding means for guiding the carriage, respectively through successive forward and upward displacements from a lower, rear position, a shelf supported on the carriage and displaceable between rear and forward positions relative to the carriage, and means including a locking device on the carriage engageable with means on the shelf for holding the shelf in its forward position and means on the supporting means engageable with said locking device at the outward limit of forward displacement of the carriage, for holding said locking device against the shelf during upward displacement of the carriage.

5. In a disappearing shelf mechanism, in combination, a movable assembly comprising a carriage and a shelf supported on the carriage and dsplaceable between rear and forward positions relative to the carriage, supporting means for guiding the movable assembly along a path of displacement extending from a lower, rear position of the carriage, to a lower, forward position of the carriage, and guiding means for guiding the assembly upwardly to an upper, forward position of the carriage, and means including co-operating stop means on the movable assembly and engageable with the supporting means at the locality of said lower forward position, for preventing rearward displacement of both the carriage and the shelf from their respective forward positions during upward displacement of the movable assembly.

6.'Apparatus as described in claim 5 wherein the stop means comprises a releasable locking element engageable between' the carriage and the shelf and -an element on the supporting means for retaining said locking element engaged when both the shelf and the carriage are at their forward positions, to prevent rearward displacement of the shelf relative to the carriage, and additional means engageable between the carriage and the guiding means upon initiation of upward movement of the carriage, to prevent rearward displacement of the carriage at regions above said lower forward position thereof.

7. Apparatus as described in claim 6 wherein the supporting means comprises horizontal track means upon which the carriage is supported for displacement between rear ,and forward positions, and the guiding means comprises vertical track means, said horizontal track means being supported for vertical displacement on said vertical track means to effect upward movement of the movable assembly, and wherein the aforesaid retaining element is disposed on the horizontal track means at the forward end of the latter, for engaging the locking element when the carriage reaches its forward position, and the aforesaid additional means comprises a vertical guide member on the vertical track means and a stop member on the carriage engageable with said guide member.

8. In a disappearing shelf mechanism, in combination, a movable assembly comprising a carriage and a shelf supported on the carriage and displaceable between rear and forward positions relative to the carriage, supporting means for guiding the movable assembly along a path of displacement extending from a lower, rear position of the` carriage, to a lower, forward position of the carriage and guiding means for guiding the assembly upwardly to an upper, forward position of the carriage, and releasable means disposed on said supporting means at the locality of said lower forward position, for normally preventing upward displacement of the movable assembly, said movable assembly including a part engageable with said releasable means at said locality to release said releasable means, and said movable assembly comprising structure including control means responsive to forward advance of the shelf relative to the carriage, for effecting engagement of said part with the releasable means only when the shelf and carriage have both been advanced to their forward positions.

9. In a disappearing shelf mechanism in combination with a carriage and supporting means and guiding means for guiding the carriage, respectively through successive forward and upward displacements from a lower, rear position, a shelf supported on the carriage and displaceable relative tothe carriage between rear and forward positions, a locking device on the carriage and cooperating means on the supporting means and held in locking position by a portion of the shelf in the rear position of the shelf, for locking the carriage in its rear position on the supporting means, said locking device being shiftable to a position releasing the carriage, upon predetermined forward displacement of the shelf relative to the carriage, said cooperating means on the supporting means, operable on initial advance of the carriage,

for further moving the locking device against another portion of the shelf to prevent rearward displacement of the shelf on the carriage, and means responsive to advancement of the carriage to its forwardmost position, for positively holding said locking device against the last-mentioned portion of the shelf throughout all upward positions of ythe carriage and shelf.

l0. in a disappearing shelf mechanism, in combination with a carriage and a supporting track upon which the carriage is displaceable forwardly from a rear position, a shelf supported on the carriage and displaceable between rear and forward positions relative to the carriage, detent means on the shelf releasable locking means on the carriage and cooperating means on the supporting track; said locking means being held in locking position by the detent means when the shelf is in its rear position, for locking the carriage against forward advance on the track, said detent means being shiftable relative to the locking means to disengage the latter upon predetermined forward displacement of the shelf relative to the carriage, and said locking means being shiftable to release the carriage, upon disengagement by said detent means.

l1. in a disappearing shelf mechanism in combination with a carriage and a supporting track upon which the carriage is displaccable forwardly from a rear position to a forward position, a shelf supported on the carriage and displaceable between rear and forward positions relative to the carriage, and locking means including an element on the carriage adapted to hold the carriage in its rearmost position, under control of the shelf, said element being shiftable to carriage-releasing position upon predetermined forward displacement of the shelf, means on the track adjacent the rear end thereof, for shifting the locking element into a further position preventing rearward displacement of the shelf relative to the carriage, in response to forward advance of the carriage from its rearmost position, said locking means including resilient means urging the locking element into said further position, and means at the forward end of the track, engageable with the locking element upon arrival of the carriage at its forward position, for positively holding said element in said further position.

l2. In a disappearing shelf mechanism having a carriage body, horizontal track means for movement of the carriage body from rear to forward positions and guide means providing upward displacement of the track means when the carriage body is in forward position, the combination of a supporting frame secured to the carriage body to constitute a carriage therewith, a shelf supported on said frame and adapted to slide between rearward and forward positions thereon, and releasable locking means intermediate the shelf, carriage and track, including cam means on the carriage engaged by the sheif and the track in its rearward position, for holding the carriage against appreciable forward displacement until the shelf has been moved to its forward position on the frame.

13. Apparatus as described in claim l2 wherein the locking means comprises retaining structure on the shelf, and wherein the cam means comprises movable cam means on the carriage, and means on the aforesaid track means for moving said cam means into engagement with the retaining structure upon advance of the carriage from its rearward position on the track means, to prevent rearward displacement of the shelf upon the frame after thc carriage has been withdrawn from its own rear position.

14. Apparatus as described in claim 13 which includes means disposed at an outward locality of the track means and engageable with the cam means on the carriage for positively holding the cam means against the retaining structure on the shelf when the carriage is advanced to its forward position.

l5. In a disappearing shelf mechanism, in combination with a carriage and a supporting track upon which the carriage is displaceable forwardly, a shelf supported on the carriage and displaceable between rear and forward positions thereon, a cam element movably mounted on the carriage, stop means on the track for engaging the cam element when the carriage is in a rearward position, and detent means on the shelf engageable with the cam element to hold the latter against the stop means for preventing forward displacement of the carriage when the shelf is in lits rear position, said detent means being displaceable with the shelf to release the cam element upon predetermined forward displacement of the shelf.

16. In a disappearing shelf mechanism, in combination with a carriage and a supporting track upon which the carriage is displaceable forwardly, a shelf supported on the carriage and displaceable between rear and forward positions thereon, a cam element movably mounted on the carriage, stop means on the track for engaging the cam element when the carriage is in a rearward position, detent means on the shelf engageable with the cam element to hold the latter against the stop means for preventing forward displacement of the carriage when the shelf is in its rear position, said detent means being displaceable with the shelf to release the cam element upon predetermined forward displacement of the shelf, and associated cam shifting means on the track engageable with the cam element upon forward advance of the carriage from said rearward position, for shifting the cam element to a further position, said shelf including cam surface means engageable by said cam element in said further position, to prevent rearward displacement of the shelf relative to the carriage.

17. Apparatus as described in claim 16 wherein the stop means and cam shifting means on the track comprise a row of teeth disposed in the path of said cam element as the carriage is advanced, said cam having a star configuration providing a plurality of projections for successive engagement with said teeth.

1.8. Apparatus as described in claim 17 which includes a further tooth on the track at a forward locality tl ereof, disposed to engage a projection of the cam element upon advance of the carriage to said locality, for positively 13 holding the cam element against the cam surface means on the shelf.

19. In a disappearing shelf mechanism, in combination with a carriage and a supporting track upon which the carriage is displaceable from a rear to a forward position, a shelf supported on the carriage and displaceable between rear and forward positions relative to the carriage, a cam element pivoted to the carriage, means on the shelf for holding the cam element in an unlocked position relative to the shelf when the shelf is in its rear position, said cam element being released from said holding means upon advance of the shelf to its forward position relative to the carriage, means on the track, operable upon forward advance of the carriage, to turn the cam element into another position when it has been released from its aforesaid unlocked position, and cam surface means on the shelf engageable by the cam element in its second position, for locking the shelf against rearward displacement on the carriage, said cam element being resliently` biased into its said second, locking position.

20. Apparatus as described in claim 19 which includes means at a forward locality of the track, engageable with said cam element upon advance of the carriage to said locality, to hold the element positively against said cam surface means on the shelf.

References Cited in the ile of this patent UNITED STATES PATENTS 

